In vehicles such as an automobile, unsprung vibration occurs during traveling and a so-called throbbing vibration occurs. As a device for suppressing the throbbing vibration, a specific damping coefficient Ct at which a sum of vectors of sprung vertical acceleration and sprung longitudinal acceleration becomes a minimum is calculated and stored in advance from a relationship of the damping coefficient of a shock absorber and the sprung vertical acceleration and a relationship of the damping coefficient of the shock absorber and the sprung longitudinal acceleration, according to Patent Literature 1. There is described an damping force control device for setting the damping coefficient of the shock absorber at a specific damping coefficient Ct when the vibration of a unsprung resonance frequency band becomes greater than a threshold value.